In an information processing system, it possibly occurs that online or batch processing terminates in an abnormal state due to a bag of a program or a failure of a storage system, and data stored in the storage system of the information processing system becomes inconsistent depending on cases. Moreover, data stored in the storage system is erased by a mistake of a human in many cases.
To restore the data of the information system in such a state, there exists a data restoration technique using data backup and restoration in which the inconsistency of data is removed to resume the processing stopped at an intermediate point thereof or the processing stopped at an intermediate point is again executed.
U.S. Pat. No. 5,263,154 describes a prior art regarding the backup and restoration. The article describes a technique in which data stored in a storage system at a point of time specified by a user is copied onto a magnetic tape without stopping data input/output (I/O) instructed from a computer (or a host) connected to the storage system (data backup) and then restores (restoration) the data using the copied data (backup data).
On the other hand, JP-A-2001-216185 describes a technique to reduce a period of time required for the restoration of data in which information of fields in which data is updated after the data backup is executed is kept as differential information. When data stored in a storage is restored using the backup data, only part of the data indicated by the differential information is used to restore the data.